1. Field of the Invention
The present invention relates to and industrial robot, and more particularly to an industrial robot to which an operation command can be easily issued.
2. Description of the Related Art
To operate an industrial robot, it is necessary to prepare a robot program for the industrial robot describing positions of operating points of the robot and/or a signal input/output for interlock with other components in the system.
A robot program describes all operations of a robot in a process in which the robot is directed to start the production, performs production activities such as welding, transferring, etc. using tools attached to the tip of the hands of the robot, and completes the production. Therefore, there may be no problems when a robot program is thoroughly executed from the start to the end of the program. However, it is difficult to perform only a part of the operations of a robot described in a robot program, to temporarily omit apart of the operations, or to stop the operation of a robot at a certain point of a first robot program to perform there a part of an operation described in a second robot program and then resume the first robot program, etc.
For example, to verify whether a robot can correctly perform each operation described in a robot program in conformance with the intentions of an operator, it may be desirable that a robot program is not executed from the beginning, but a portion of the operation to be verified is repeatedly performed a number of times. To do this, the program counter of a robot program is forcibly moved to the position where operation is to be started hereafter, a verification is made at this position for the current position of the robot, the status of an I/O signal, the value of a register, etc., they are manually changed so that the current position of the robot, the status of the I/O signal, and the value of the register are the same as those assumed when the robot program is executed from the beginning, and then the robot program is resumed and the operation to be verified is performed by the robot. To make a verification on the same operation again, the above-mentioned operation must be repeated.
When a robot program is continuously performed from the start to the end of it, and when an attempt is made to temporarily stop the robot program, and then perform it from the beginning, if, for example, the robot program is suddenly stopped while the robot is carrying a heavy object, then there may be a problem that interference with surrounding equipment occurs by dropping a carried object and/or the displacement of an operation path. Therefore, the operator is required to stop the robot program at a stop timing determined by the operator.
When a robot holds a heavy workpiece, but the workpiece is still placed on the worktable, there may be no problem if a signal is manually output to open the hand of the robot to the hand holding the workpiece. However, if the hand is opened with the workpiece lifted from the worktable, then the workpiece may be dropped. Therefore, when the operator manually outputs a signal, he or she carefully considers the status of the robot before issuing an open hand command.
For an industrial robot operated in a spot-welding line, if an alarm is given to the robot operated in the welding operation on the inside of a car using a welding gun, and it is determined based on the cause of the alarm that it is not possible to resume the robot program, then the welding gun is fully opened first, the robot is manually moved to set the welding gun outside the car to the point where the robot and the car do not interfere with each other, and it is necessary to execute the robot program again from the beginning. In the spot-welding line, normally a plurality of robots are operated, and the robots are interlocked using I/O signals, etc. to avoid the interference between robots. Therefore, another robot may be waiting for the completion of the spot-welding operation of the robot in which an alarm is occurred. In this case, after manually moving the robot to the position where there is no interference between robots, it is necessary to issue an interlock signal after the manual completion of the welding operation. After an alarm is given and the robot is stopped, manual recovery is required to recover the robot and to resume the operation of the line.
Furthermore, when an alarm is given in a production line, the contents of the alarm is understood to identify the cause of the alarm, the alarm code is verified on a teaching pendant of the robot to remove the cause of alarm, the meaning of the alarm code is examined referring to a robot manual, the parts that may contribute to the alarm is identified, and then the status signal for the parts is checked on the teaching pendant. Practically, it is difficult to immediately identify the parts that may contribute to the alarm, and check the statuses of the parts, and it is necessary to check each of a large number of parts that may contribute to the alarm in order of possibility from the highest to the lowest so that a part which causes the alarm can be located. In checking the parts, it is necessary to display a screen of the status signal on the teaching pendant to check the status signal.
Even when the cause of the alarm has been known and removed and the robot program is resumed from the alarm-causing point, the robot has coasted due to an emergency stop when an alarm is given. Therefore, if the program is resumed as it is, the robot will not follow the taught operation path, thereby causing the problem that the robot interferes with surrounding equipments, jigs, etc. To correctly resume the program, the robot has to be manually moved onto the original operation path before resuming the program.
As described above, in the conventional techniques, it is difficult to perform only a part of the operations of a robot described in a robot program, to temporarily omit a part of the operations, or to stop the operation of a robot at a certain point to perform there an operation not described in the robot program and then resume the robot program safely and easily. Furthermore, to verify that the robot can perform the operations correctly, it is desirable that a relevant part is repeatedly performed, but it is not easy to perform such operations.
When a robot program is stopped, it is necessary to determine the situation, and carefully consider the stop timing. When a robot is manually operated using an open hand command, it is also necessary to carefully check the current situation of the robot to avoid an undesired operation. When an alarm is given to terminate the robot program halfway, an operator must perform the operation necessary for terminating the program according to circumstances.
Furthermore, to identify the cause of an alarm, the operator has to check the status of all of a number of parts that may contribute to the alarm on a teaching pendant. When the program is resumed after the issue of alarm, the operator has to determine a necessary operation to resume the program according to circumstances, and to resume the robot operation after performing the necessary operation.
To allow a robot to perform an operation, it is necessary for an operator to manually perform required operations based on the teaching pendant or the like before causing the robot to perform the operation. That is, the operator does not allow the robot to freely perform an operation. Instead, he or she first determines, according to the status of the robot, additional operations required for accomplishing the operation or divisions of the additional operations into smaller operations before carrying out the operation, and then performs a number of smaller operations by manual operation on a teaching pendant or by executing a robot program. That is, the operator cannot directly issue an operation command to the robot. The operation which the operator originally desired to perform cannot be performed by a robot.
As a result, when an unskilled operator operates a robot, he or she cannot check up correct and necessary operation, and therefore it is not possible to cause the robot carry out a required operation. Even when the operation can be correctly analyzed, some operations must be manually performed on a teaching pendant, some operations must be performed by executing a robot program, thereby requiring different means for performing an operation. Therefore, an operator who cannot correctly determine means for performing an operation cannot allow a robot to perform a requested operation. That is, an operator who can correctly operate a robot has to correctly determine means for performing an operation, requiring expertise. Thus, there is a problem that every operator cannot correctly operate a robot.